Synthesis of Markovnikov vinyl sulfides via dinuclear Rh(i)-phosphine catalyzed hydrothiolation of alkynes in aqueous media

Article abstract of DOI:10.1039/c3ra44499f

An efficient and green procedure for the synthesis of Markovnikov i.e. branched vinyl sulfides in aqueous media was developed by employing the dinuclear Rh(i) complexes of hydrophilic phosphines as catalysts in the alkyne hydrothiolation with aliphatic thiols. Deuterium-labeling studies provide evidence for the aptness of these dinuclear catalysts to form selectively the Markovnikov syn-addition products. Catalyst order experiments disclose that the order with respect to the concentration of the catalyst is one, i.e. in solution the active catalyst is dinuclear with one active metal center and the second metal center contribute the cooperative effects to influence the Markovnikov selectivity in hydrothiolation. Further, the possibility of catalyst recovery and recycling experiments were also demonstrated.

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Graphical Abstract
Synthesis of Markovnikov vinyl sulfides via dinuclear Rh(I)-phosphine catalyzed
hydrothiolation of alkynes in aqueous media
Shravankumar Kankala, Srinivas Nerella, Chandra Sekhar Vasam* and Ravinder Vadde*
An efficient regioselective and recyclable hydrothiolation procedure for the synthesis of
Markovnikov vinyl sulfides in aqueous media was developed by employing the water-
soluble dinuclear Rh(I)-Phosphine catalysts.Catalyst order experiments were used to
describe the cooperative effects between the two metal centers in dinuclear catalysts.
SR2
R1
[Rh(µ-X)(CO)(L)]2
R2SH
Thiol
R1
aqueous-THF, rt, 0.5 h
Alkyne
Branched
Vinyl Sulfide
L = Hydrophilic Phosphine
X = anionic ligand

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ARTICLE TYPE
Synthesis of Markovnikov vinyl sulfides via dinuclear Rh(I)-phosphine
catalyzed hydrothiolation of alkynes in aqueous media
Shravankumar Kankala,a Srinivas Nerella,a Chandra Sekhar Vasam*b and Ravinder Vadde*a
5
Received (in XXX, XXX) Xth XXXXXXXXX 20XX, Accepted Xth XXXXXXXXX 20XX
DOI: 10.1039/b000000x
An efficient and green procedure for the synthesis of Markovnikov i.e. branched vinyl sulfides in aqueous
media was developed by employing the dinuclear Rh(I) complexes of hydrophilic phosphines as catalysts
in the alkyne hydrothiolation with aliphatic thiols. Deuteriumꢀlabeling studies provide evidence for the
10 aptness of these dinuclear catalysts to form selectively the Markovnikov synꢀaddition products. Catalyst
order experiment discloses that the order with respect to the concentration of the catalyst is one i.e. in
solution the active catalyst is dinuclear with one active metal center and the second metal center
contribute the cooperative effects to influence the Markovnikov selectivity in hydrothiolation. Further, the
possibility of catalyst recovery and recycling experiments were also demonstrated.
15 Introduction
Results and Discussion
Hydrothiolation of alkynes with aryl/aliphatic thiols driven by
radical,1 nucleophilic2 and metalꢀcatalyzed3 methods is useful to
produce synthetically and biologically valuable vinyl sulfides.
While the alkyne hydrothiolation proceeds via radical method
Previously we have reported6 the synthesis of some
hydrophilic phosphines and their dinuclear Rh(I) complexes
[Rh(ꢁꢀX)(CO)(L)]2 (X = bridging/chelating, L = hydrophilic
20 forms exclusively the antiꢀMarkovnikov (linear) products, the 40 phosphine) (see Figure 1) and their application as catalysts for
nucleophilic and metalꢀcatalyzed methods form either antiꢀ
Markovnikov or Markovnikov (branched) product (Scheme 1).
Nevertheless, the metal catalyzed hydrothiolation was found to be
more flexible than other methods to tune the regioselectivity.3ꢀ5
regioselective
hydroformylation,
isomerization
and
hydrogenation of olefins in mono and biphasic aqueous media.
Further, our curiosity in designing the dinuclear Rh(I) catalysts is
also to highlight the role of possible cooperative effects between
25
The steric and electronic properties of the ligand of the metal 45 two metal centers7 on the rate and selectivity of a organic
catalyst have found to play key role to mediate and direct the
addition of SꢀH bond across CꢀC triple bonds and thereby the
product regioselectivity. In this line, a challenging objective is the
development of a catalytic system for the hydrothiolation of
transformation. In this context, we are now intended to explore
the application of these dinuclear Rh(I)ꢀphosphine catalysts in the
hydrothiolation of alkynes in aqueous media. Besides the
regioselectivity, it is also important to optimize the
30 alkynes with aliphatic thiols to furnish the Markovnikov 50 hydrothiolation reaction conditions by using a water soluble
products,4 which are difficult to synthesize by other methods.
recyclable homogeneous Rh(I)ꢀcatalyst to address the
environmental concerns and the cost of precious metal catalyst as
well.
Herein we describe the regioselective Markovnikov
55 hydrothiolation of terminal alkynes with aliphatic thiols that
catalyzed by dinuclear Rh(I)ꢀphosphines in aqueous media. Three
different series of bridging dinuclear Rh(I)ꢀphosphine catalysts,
SR2
Radical
R1
SR2
R1
Linear Products
R1
R2SH
SR2
R2S
[Rh(ꢁꢀX)(CO)(L)]2 (X
= anionic bridging ligands, viz.,
Nucleophilic (or)
MetalꢀCatalyst
R1
SR2
pyrazolato (pz), 3,5ꢀdimethyl pyrazolato (dmpz), 7ꢀazaindolato
60 (aza), and thiophenolato (SPh); and L = hydrophilic phosphine)
(Figure 1) were investigated as catalysts in this reaction to make a
comparison in the catalytic activity and stability. An effort to
successful catalyst recycling experiments of hydrothiolation in
aqueous media was also emphasized.
R1
Branched/Linear Products
R1
Scheme 1 Hydrothiolation of terminal alkynes.
35
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2L
[Rh(ꢀꢀX)(CO)2]2
1-4
[Rh(ꢀꢀX)(CO)(L)]2
19a as the major product in good yields (Table 1, Entries 7, 8, 13ꢀ
45 16) in shorter reaction times. The products characterization data
was given in experimental section. Only a trace amount (2ꢀ6%) of
linear product was detected in all the experiments, which can be
separated by column chromatography. Further, there was no
indication for the disulfide byproduct formation in the above
50 hydrothiolation. This is a quite opposite result than that observed
with the two dinuclear Rh(I) precursors [Rh(ꢂꢀX)(CO)2] (1 & 4)
those without phosphine and clearly specify that the steric and
electronic properties of strong σꢀbasic phosphine ligands used in
this work are beneficial to control the hydrothiolation catalytic
55 path and thereby the regioselectivity. Further, no byꢀproducts
such as disulfide or bis(thio)alkenes were observed in this work.
ꢀ2CO
5-16
X = pz (1), dmpz (2), aza (3), SPh (4),
L1 = P(C6H5)2C6H4ꢀ3ꢀCOOH, L2 = P(C6H5)2C6H4ꢀ2ꢀCHO,
L3 = P(C6H5)2ꢀ2ꢀC5H4N, L4 = P(C6H5)2C6H4ꢀ2ꢀCH2OH
Ph
R
R
OC
L
S
N
N
OC
L
L
OC
L
L
L
N
N
N N
N N
Rh
Rh
Rh
Rh
Rh
Rh
S
CO
CO
CO
R
R
Ph
5-8
13-16
9-12
L = L1 (9), L = L2 (10)
L = L3 (11), L = L4 (12)
R = H, L = L1 (5)
R = H, L = L2 (6)
L = L1 (13), L = L2 (14)
L = L3 (15), L = L4 (16)
R = Me, L = L1 (7)
R = Me, L = L2 (8)
Table
1 Hydrothiolation of phenylacetylene (17a) with
benzylthiol (18a) catalyzed by different Rh(I)ꢀphosphine catalysta
Figure 1 Dinuclear Rh(I)ꢀcomplexes (5ꢀ16) formed with hydrophilic
S
phosphines.
2 mol % cat
SH
water:THF(7:3), rt
Among the dinuclear Rh(I)ꢀphosphine catalysts used in this
work, the synthesis and structural analysis (including crystal) of
transꢀ[Rh(ꢁꢀpz)(CO)(L)]2, [Rh(ꢁꢀdmpz)(CO)(L)]2 and [Rh(ꢁꢀ
aza)(CO)(L)]2 series and the hydrophilic phosphines (L1-L4) were
synthesized according to the methods described by us
previously.6 The synthesis of transꢀ[Rh(ꢁꢀSPh)(CO)(L)]2 is given
19a
5
17a
18a
LꢀE/Bb
Entry Catalyst
Conversion
Time (h)
11/89c/0
58/11c/31
63/9c/28
1
2
3
4
No Catalyst
16
7
57
1
4
76
7
82
10 in experimental section.
1 + Radical trap
59ꢀ62/11ꢀ10c/30ꢀ28d
7
77ꢀ79
All the hydrothiolation reactions investigated in this work were
carried out in aqueous THF (7:3) solvent system to avoid the
solubility problems of the substrates and products, and to develop
a recyclable catalyzed system. Initially, the hydrothiolation of
15 phenylacetylene (17a) with benzyl thiol (18a) was studied with
and without the dinuclear Rh(I)ꢀphosphine catalysts. A blank
hydrothiolation experiment without the catalyst was occurred
only under refluxing conditions (16 hrs) and formed the mixture
of linear vinyl sulfide, in which the Zꢀisomer was the major
20 product (Table 1, entry 1), probably via a radical method as
described by others.1,4i
Based on this observation, in order to examine the role of
Rh(I) catalyst on product regioselectivity, firstly the two
dinuclear Rh(I) tetracarbonyl precursors [Rh(ꢂꢀX)(CO)2]2 (1 & 4,
25 Figure 1), those without phosphine ligand, were employed as
catalysts. It was noticed that the catalysts 1 and 4 were
accomplished the hydrothiolation at room temperature (RT = 25
°C) only (7 hrs), but formed the mixture of both linear and
branched products. However, this time Eꢀisomer of linear vinyl
30 sulfide was the major product (entry 2 & 3). Addition of the
radical traps (i) 2,6ꢀdiꢀtertꢀbutylꢀ4ꢀmethylphenol (BHT), (ii) 4ꢀ
methoxyphenol and (iii) 2,2,6,6ꢀTetramethylpiperidinꢀ1ꢀyl)oxyl
(TEMPO) to this reaction in the presence of catalyst 1 at room
temperature did not change the activity or the selectivity (entry
35 4). This result indicates that at room temperature the
hydrothiolation was mediated by a catalytic path, but not by
radical intermediate path.
5
10/90
5
0.6
89
6
9/91
4/96
9/91
10/90
8/92
9/91
10/90
3/97
8/92
9/91
6
0.6
0.5
0.5
0.7
0.7
0.7
0.7
0.5
0.5
0.5
0.5
87
94
90
89
87
87
88
96
92
90
92
7
7
8
8
9
9
10
11
12
13
14
15
16
10
11
12
13
14
15
16
a
8/92
1
13
b
All products were characterized by H/ C NMR and mass spectral analysis. Isolated
c
yields after column chromatography of Linear (LꢀE) and Branched (B) Products. Yield
d
of LꢀZ. Radical traps (2 mol%) (i) BHT, (ii) 4ꢀmethoxyphenol and (iii) TEMPO.
60
Deuteriumꢀlabeling hydrothiolation experiment (Scheme 2)
was conducted in d8ꢀTHF to provide evidence for the assistance
65 by Rh(I)ꢀphosphine catalyst 13 in the process of Markovnikov
synꢀaddition. Upon the synthesis of 1,1ꢀdisubstituted deuterated
vinyl sulfide, and in reference to the previous works by Ogawa4c
and Love5a we propose that firstly the catalyst 13 facilitate the
oxidative addition of thiol to form the active HꢀRhꢀSR species in
70 the presence of neutral phosphine ligand. After this, the alkyne
migratory insertion occurs into the RhꢀS bond in a Markovnikov
synꢀaddition fashion followed by reductive elimination pathway
to produce 1,1ꢀdisubstituted deuterated vinyl sulfide without
deuterium exchange but not due to the external nucleophilic
After the above effort, the dinuclear Rh(I)ꢀphosphines of the
type [Rh(ꢂꢀX)(CO)(L)]2 (5ꢀ16, Figure 1) were employed as
40 catalysts in the same hydrothiolation. The results of Table 1
(Entries 5ꢀ16) reveal that the Rh(I)ꢀphosphine (5-16) have
efficiently directed the sharp reversal in the regioselectivity of
hydrothiolation of 17a with 18a to give the branched vinyl sulfide
1
75 attack. The characteristic H NMR signal for deuterated prouct
was found at 5.14 ppm. Catalyst mediated alkyne insertion into
metalꢀheteroatom bond MꢀX (X = Si,8 N9) has also been reported.
This information indicates the influence of steric and electronic
properties of the catalyst on product regioselectivity.4i Further
2
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discussion is provided along with catalyst cycle (see Scheme 3).
Ph
Table 2 Hydrothiolation between variety of terminal alkynes and
thiols catalyzed by Rh(I)ꢀphosphine catalyst (13)a
S
SR2
2 mol % cat 13
H
2 mol % cat (13)
Ph SH
R1
Alkyne
R2SH
Thiol
D
d8ꢀTHF, rt
R1
Branched
aqueousꢀTHF, rt, 0.5 h
D
Vinyl Sulfide
5
Scheme 2 Reaction between deuteriumꢀlabeled phenylacetylene with
Entry
Product Yield (%)b
Alkyne
Thiol
benzylthiol.
SH
1
(17a)
(17b)
(18a) 19a
96
80
Regarding the stability of catalyst during the hydrothiolation,
LC Mass analysis of the spent catalysts (7 & 13) show that there
10 was no decomposition in their dinuclear structure in solution.
This observation support the concept that all the four bridging
ligands used in this work (see Figure 1) have good potential to
bind the two Rh(I) metal centers also in solution during catalytic
reactions.
2
18a
19b
CH3
(17c) 18a
19c
19d
96
98
3
4
H3C
H3CO
F3C
15
To determine the cooperative effects between two metal
centers in the dinuclear catalyst i.e. whether the active catalyst is
dimeric with two active centers, monomeric, or dimeric with one
active center in solution, we have also included a catalyst order
experiment. We have studied the hydrothiolation process with
18a
(17d)
(17e) 18a
19e
19f
19g
5
85
84
86
20 different concentrations of the dinuclear catalyst 13 (between 0.5ꢀ
2.0 mol %) and analyzed the yields of the product 19a after a
constant time intervals. The results are provided in the ESI. This
data indicates that as the concentration of catalyst increases the
yields are increasing proportionally. This suggests that the order
25 with respect to the concentration of the catalyst is one. This is an
evidence that the active catalyst is dinuclear with one active metal
center and the second metal center contribute the cooperative
effects to influence the Markovnikov selectivity in
hydrothiolation.
(17f)
18a
18a
6
7
Br
PhO
(17g)
OAc
O
AcO
AcO
SH
17a
19h
90
8
OAc
(18b)
18b
18b
17c
17e
19i
19j
93
88
9
10
30
On the other hand, a mono nuclear Rh(I)ꢀPhosphine [Rh(quinꢀ
8ꢀO)(CO)(P(C6H5)2C6H4ꢀ3ꢀCOOH)], also reported by us
previously,10 catalyzed the hydrothiolation of 17a with 18a and
gave a mixture of regioisomers, with linear Eꢀisomer as major (Lꢀ
E=52%, LꢀZ=13%, B=35%).
92
94
87
(18c)
19k
19l
11
12
13
SH
17a
17d
17e
18c
18c
18c
19m
35
The next study in this work was to extend the above optimized
hydrothiolation protocol towards a variety of aryl/alkyl terminal
alkynes and aliphatic thiols including thiosugars those having
different steric and electronic properties as shown in Table 2.
These reactions were investigated in the presence of Rh(I)ꢀ
90
84
19n
19o
14
15
17f
(17h) 18a
(H3C)3C
91
16
17a
SH (18c)
19p
SH
90
17
17a
(18a)
19q
40 phosphine catalyst (13). The results of Table 2 indicate that
under the optimized conditions, catalyst (13) favoured the
formation of branched vinyl sulfides (19b-q) as major product in
all the reactions. Nevertheless, the influence of electronic effects
on the product yield was clearly noticed in all the reactions
45 investigated. For example, the hydrothiolation of 18a with
different alkynes (17b-h) has shown a variation in the total yield
of the product with respect to the position and nature of
substituent on alkynes. The alkynes those having an electron
donating substituent at para position have provided relatively
50 better yields (Table 2, Entries 3, 4, 9 & 12) than those having
electron donating substituent at ortho position (entry 2). On the
other hand, the alkynes those having an electron withdrawing
substituent at para position have provided less yields due to the
electronic effect (Entries 5, 10 & 13). The hydrothiolation of
55 thiosugar 18b with the alkynes 17a, 17c and 17e has also shown
similar effect on product yields (Entries 8ꢀ10).
aAll products were characterized by 1H/13C NMR and mass spectral analysis.
bIsolated yield after Column Chromatography .
60
With reference to the results presented in Table 1 and 2,
deuteriumꢀlabeling study, catalyst order experiment and by taking
the literature support, we made an effort to draw an appropriate
reaction mechanism for the dinuclear Rh(I)ꢀphosphine catalyzed
65 hydrothiolation. The reports by Love4e,g and Oro4i indicate that
the appropriate ligand choice in mono/diꢀnuclear Rh(I) catalyst
could reverse the regioselectivity in hydrothiolation. Love’s
report show that the electron rich mononuclear Rh(I)
pyrazolylborate complex catalyzed the alkyne hydrothiolation to
70 give branched vinyl sulfides. Oro’s4i report described the ligand
controlled regioselective hydrothiolation using both mono and
dinuclear Rh(I)ꢀNꢀheterocyclic carbene (Rh(I)ꢀNHC) catalysts in
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toluene. The formation of active HꢀRhꢀSR species, how the steric
and electronic properties of the NHC and hydride ligands are
hydrothiolation using Pd, Ni, Rh and Zr catalysts.4 High
Markovnikov selectivities with Pd catalysts were reported only
beneficial to govern the coordination position of labile ligands 50 under microwave conditions, which however is not a recyclable
and substrates (i,e. positioning of alkyne cis to thiolate and trans
to hydride) in the HꢀRhꢀSR species to favour alkyne insertion into
RhꢀS instead of RhꢀH and thereby reversal in regioselectivity to
form the branched products was evaluated. The HꢀRhꢀSR was
method.4a A plausible mechanism has been proposed in our work
by considering the deuteriumꢀlabeling study and catalyst order
experiment to furnish selectively the Markovnikov vinyl sulfides.
5
also found to be useful to prevent the formation of disulfide and 55 Acknowledgments
bis(thio)alkenes byꢀproduct in the hydrothiolation.4i We have also
10 not observed any such byꢀproducts in our work.
One of the authors Dr. S. Kankala thanks CSIR, New Delhi for
the award of Research Associate.
A plausible hydrothiolation catalytic cycle of present work
depicted in Scheme 3 starts with thiol addition to the Rh(I)
catalyst, followed by migratory insertion of alkynes into RhꢀSR
bond and reductive elimination to furnish the branched vinyl
15 sulfide product. As observed in kinetic order experiments, there is
only one Rh(I) center is shown as active in the dinuclear catalyst.
Deuterium labelling experiments supported the assistance by
60
Experimental Section
General
dinuclear Rh(I)ꢀPhosphines in the formation of Markovnikov synꢀ 65 All commercially available reagents were used without further
addition product. The phosphine ligands used in the present work
20 are also powerful σꢀdonor ligands and bulky to direct the
coordination of labile ligands, substrates in the Rh(I) coordination
sphere i.e. the position of alkyne cis to thiolate and trans to
purification. The solvents were dried and deoxygenated by
refluxing and storing them over sodium. The phosphines were
prepared according to methods reported[6] by us and others. All
the synthetic reactions were carried out in a nitrogen atmosphere
hydride in [Rh(L)H(SR)(ꢁꢀX)2(CO)(L)Rh] to favour the 70 using the schlenk technique. Purity of the compounds was
formation of branched vinyl sulfide products.
checked by TLC using Merck 60F254 silica gel plates. Elemental
analyses were obtained with an Elemental Analyser PerkinꢀElmer
240C apparatus. Bruker WH 270 NMR and Brucker SXPꢀ100
25
The reusability of a catalyst is one of the important strategies
and makes it useful for commercial applications. In this respect,
catalyst recovery and recycling experiments were studied using
1
instruments were used to record H, 13C and 31PꢀNMR spectra;
the Rh(I)ꢀphosphine catalyst (13) in the hydrothiolation of alkyne 75 chemical shifts were referenced to TMS. EI (electron impact)
17a with thiol 18a. After the first catalytic run, the organic mass spectra (at an ionising voltage of 70 eV) were obtained
using Shimadzu QP5050A quadrupoleꢀbased mass
spectrometer. IR spectra were recorded on Nicoletꢀ740
spectrophotometer and PerkinꢀElmer 580B spectrophotometer.
30 reaction mixture was extracted into ethyl acetate and the aqueous
layer containing the spent Rh(I)ꢀphosphine catalyst (13) were
reused successively up to five runs under same experimental
conditions (i.e. 2 hrs at RT). The desired product 19a was
obtained in 85% even after fifth catalytic run (ESI) with constant
35 selectivity using the spent catalyst.
a
a
80
General
Procedure
for
the
synthesis
catalyst
of
(13).
[Rh(µ-
To
SPh)(CO)(P(C6H5)2C6H4-3-COOH)]2
a
dichloromethane solution of [Rh(ꢂꢀCl)(CO)2]2 (0.194 g, 0.5 mmol), 0.132
g (1 mmol) of aqueous solution of sodium thiophenolate was added
H
X
X
X
X
L
L
RSH
Rh
Rh
85 followed by 0.306 g (1 mmol) of (3ꢀcarboxyphenyl)diphenylphosphine.
The reaction mixture was stirred for a period of 2 h until the red colored
reaction mixture instantaneously changed to light brown with the
evolution of carbon monoxide. Later the reaction mixture was
concentrated to small volume to which diethyl ether was added to
90 crystallize the title product as a brown semi crystalline solid. This solid
was filtered by suction, washed with ether and dried in vacuum: 1H NMR:
δ 10.84 (s, COOH, 2H), 6.95ꢀ8.32 (m, ArꢀH, 38H) ppm. 13C NMR: δ
180.10 (CO), 176.40 (COOH), 142.82 (CꢀS), 128.32ꢀ140.45 (ArꢀC) ppm.
FTIR: 1976 (RhꢀCO), 1696 (COOH), 656 (CꢀS), 536 (RhꢀP), 415 (RhꢀS)
95 cmꢀ1. EA calcd (%) for C52H40O6P2Rh2S2: C 57.19, H 3.62, S 5.85; found
C 57.13, H 3.59, S 5.82.
Rh
Rh
CO
SR
SR
R1
R1
RSH
H
X
X
L
H
Rh
Rh
X
L
SR
R1
SR
R1
Rh
Rh
X
Scheme 3 Possible mechanism for the formation of branched alkyl vinyl
40 sulfides.
[Rh(µ-SPh)(CO)(P(C6H5)2C6H4-2-CHO)]2 catalyst (14). 1H NMR: δ
10.60 (br, CHO, 2H), 6.70ꢀ8.55 (m, ArꢀH, 38H) ppm. 13C NMR: δ 176.30
100 (CO), 174.83 (CHO), 141.51 (CꢀS), 127.40ꢀ139.85 (ArꢀC) ppm. FTIR:
1980 (RhꢀCO), 1680 (CHO), 654 (CꢀS), 510 (RhꢀP), 390 (RhꢀS) cmꢀ1. EA
calcd (%) for C52H40O4P2Rh2S2: C 58.73, H 3.81, S 6.08; found C 58.71,
H 3.76, S 6.06.
Conclusions
We have optimized for the first time both the regioselective and
recyclable hydrothiolation catalytic conditions for the synthesis
of Markovnikov vinyl sulfides in aqueous media at room
45 temperature using waterꢀsoluble dinuclear Rh(I)ꢀPhosphine
catalysts. The results obtained in our work are comparable or
relatively better than the existing reports on Markovnikov alkyne
4
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DOI: 10.1039/C3RA44499F
[Rh(µ-SPh)(CO)(P(C6H5)2-2-C5H4N)]2 catalyst (15). 1H NMR: δ 6.75ꢀ
8.56 (m, ArꢀH, 38H) ppm. 13C NMR: δ 178.52 (CO), 159.75 (C=N),
141.73 (CꢀS), 127.65ꢀ139.80 (ArꢀC) ppm. FTIR: 1969 (RhꢀCO), 650 (Cꢀ
S), 505 (RhꢀP), 410 (RhꢀS) cmꢀ1. EA calcd (%) for C48H38N2O2P2Rh2S2: C
57.25, H 3.78, N 2.72, S 6.36; found C 57.23, H 3.74, N 2.71, S 6.34.
C16H16OS: (256.09): calcd. C 74.96, H 6.29, S 12.51; found C 74.94, H
60 6.28, S 12.49.
Benzyl(1-(4-trifluoromethylphenyl)vinyl)sulfane (19e). Yield (85%),
Pale yellow oil. 1H NMR (400 MHz, CDCl3): δ 3.90 (s, 2H), 5.24 (s, 1H),
5.46 (s, 1H), 7.22ꢀ7.32 (m, 5H, ArꢀH), 7.41 (d, 2H, J = 7.2 Hz, ArꢀH),
5
[Rh(µ-SPh)(CO)(P(C6H5)2C6H4-2-CH2OH)]2 catalyst (16). 1H NMR: δ 65 7.82 (d, 2H, J = 7.2 Hz, ArꢀH) ppm. 13C NMR (100 MHz, CDCl3): δ
2.56 (br, OH, 2H), 2.84 (s, CH2, 2H), 6.75ꢀ8.59 (m, ArꢀH, 38H) ppm. 13
C
37.32, 112.90, 120.46, 122.65, 127.4, 128.7, 129.0, 131.7, 136.9, 138.5,
144.0 ppm. MS (EI, 70 eV): m/z (%) = 295 [M+H]+. EA calcd (%) for
C16H13F3S: (294.07): calcd. C 65.29, H 4.45, S 10.89; found C 65.25, H
4.42, S 10.86.
NMR: 180.14 (CO), 141.05 (CꢀS), 65.60 (ꢀCH2), 127.35ꢀ139.80 (ArꢀC)
10 ppm. IR: 1940 (Rhꢀ(CO)), 3410 (OH), 665 (CꢀS), 525 (RhꢀP), 385 (RhꢀS)
cmꢀ1. Anal. Calc. For C52H44O4P2Rh2S2: C, 60.41; H, 4.29; S, 6.20;.
Found: C, 60.34; H, 4.14; S, 6.02%.
70
Benzyl(1-(4-bromophenyl)vinyl)sulfane (19f). Yield (84%), Pale yellow
oil. 1H NMR (400 MHz, CDCl3): δ 3.88 (s, 2H), 5.23 (s, 1H), 5.44 (s,
1H), 7.22ꢀ7.32 (m, 5H, ArꢀH), 7.41 (d, 2H, J = 8.7 Hz, ArꢀH), 7.48 (d,
2H, J = 8.7 Hz, ArꢀH) ppm. 13C NMR (100 MHz, CDCl3): δ 37.32,
General Procedure for the catalytic hydrothiolation of terminal
15 alkynes with thiols
Dinuclear Rh(I)ꢀphosphine catalyst (13) (0.20 mmol, 2 mol %), water (7
mL), THF (3 mL), thiol (11 mmol) and alkyne (10 mmol) were combined 75 112.90, 122.65, 127.45, 128.72, 129.04 (two peaks overlaping), 131.76,
in a 50 mL round bottom flack equipped with a magnetic stir bar. The
reaction was stirred at room temperature for 30 minutes. After the
20 reaction was completed, the resulting mixture was diluted with
dichloromethane (50 mL). The organic layer was separated and the
aqueous layer was reused in next calaytic cycle. The organic layer was
dried (anhydrous Na2SO4) and evaporated under reduced pressure to
afford a crude product, which was subjected to column chromatography
25 (silica gel, 60ꢀ120 mesh, eluent; nꢀhexane:EtOAc gradient) to afford pure
compounds (19a-q).
136.92, 138.50, 144.20 ppm. MS (EI, 70 eV): m/z (%) = 305 [M+H]+. EA
calcd (%) for C15H13BrS: (303.99): calcd. C 59.02, H 4.29, S 10.51; found
C 59.12, H 4.32, S 10.49.
80 Benzyl(phenoxymethylvinyl)sulfane (19g). Yield (86%), Pale yellow
oil. 1H NMR (400 MHz, CDCl3): δ 4.01 (s, 2H), 4.58 (s, 2H), 5.12 (s,
1H), 5.48 (s, 1H), 6.89ꢀ6.99 (m, 5H, ArꢀH), 7.24ꢀ7.39 (m, 5H, ArꢀH)
ppm. 13C NMR (100 MHz, CDCl3): δ 37.54, 71.68, 112.20, 115.65,
122.15, 128.34, 129.62, 129.90, 130.45, 137.52, 141.91, 159.35 ppm. MS
85 (EI, 70 eV): m/z (%) = 257 [M+H]+. EA calcd (%) for C16H16OS:
(256.09): calcd. C 74.96, H 6.29, S 12.51; found C 74.97, H 6.30, 12.50.
1
Benzyl(1-phenyl)sulfane (19a). Yield (96%), Yellow oil. H NMR (400
MHz, CDCl3): δ 3.62 (s, 2H), 5.06 (s, 1H), 5.31 (s, 1H), 6.92ꢀ7.14 (m,
30 8H, ArꢀH), 7.50 (m, 2H, ArꢀH) ppm. 13C NMR (100 MHz, CDCl3): δ
37.24, 111.56, 127.23, 127.60, 128.52, 128.64, 129.14, 129.65, 137.42,
2,3,4,6-Tetra-O-acetyl-1-thio-β-D-glycopyranoside(1-
phenylvinyl)sulfane (19h). Yield (90%), Yellow oil. 1H NMR (400
139.94, 145.62 ppm. MS (EI, 70 eV): m/z (%) = 227 [M + H]+. EA calcd 90 MHz, CDCl3): δ = 2.02, 2.05, 2.09, 2.12, (4s, 12H), 3.82 (ddd, J = 10.1,
(%) for C15H14S: (226.08): calcd. C 79.60, H 6.23, S 14.17; found C
79.58, H 6.22, S 14.15.
4.8, 2.4 Hz, 1H), 4.15 (dd, J = 12.4, 2.4 Hz, 1H), 4.28 (dd, J = 12.5, 4.8
Hz, 1H), 4.85 (d, J = 10.2 Hz, 1H), 5.10 (t, J = 9.1 Hz, 1H), 5.12 (t, J =
9.4 Hz, 1H), 5.29 (t, J = 9.3 Hz, 1H), 5.32 (s, 1H), 5.34 (s, 1H), 7.37 (m,
3H, ArꢀH), 7.60 (m, 2H, ArꢀH) ppm. 13C NMR (100 MHz, CDCl3): δ =
35
Benzyl(1-o-tolylvinyl)sulfane (19b). Yield (80%), Pale yellow oil. 1H
NMR (400 MHz, CDCl3): δ 2.38 (s, 3H), 3.91 (s, 2H), 5.15 (s, 1H), 5.34 95 20.04, 20.22, 61.42, 67.75, 69,42, 73.25, 75.50, 80.66, 110.92, 126.54,
(s, 1H), 7.22ꢀ7.36 (m, 9H, ArꢀH) ppm. 13C NMR (100 MHz, CDCl3): δ
127.42, 128.04, 134.42, 152.42, 169.91 ppm. MS (EI, 70 eV): m/z (%) =
489 [M + Na]+. EA calcd (%) for C22H26O9S: (466.13): calcd. C 56.64, H
5.62, S 6.87; found C 56.62, H 5.58, S 6.82.
20.72, 37.91, 112.53, 126.62, 128.20, 129.10, 129.52, 129.94, 130.52,
40 131.30, 137.12, 138.04, 140.40, 145.92 ppm. MS (EI, 70 eV): m/z (%) =
241 [M + H]+. EA calcd (%) for C16H16S: (240.10): calcd. C 79.95, H
6.71, S 13.34; found C 79.94, H 6.70, S 13.32.
100 2,3,4,6-Tetra-O-acetyl-1-thio-β-D-glycopyranoside(1-o-
tolylvinyl)sulfane (19i). Yield (93%), Yellow oil. 1H NMR (400 MHz,
CDCl3): δ = 2.02, 2.05, 2.09, 2.12, (4s, 12H), 2.40 (s, 3H), 3.82 (ddd, J =
10.1, 4.8, 2.4 Hz, 1H), 4.15 (dd, J = 12.4, 2.4 Hz, 1H), 4.28 (dd, J = 12.5,
4.8 Hz, 1H), 4.85 (d, J = 10.2 Hz, 1H), 5.10 (t, J = 9.1 Hz, 1H), 5.12 (t, J
1
Benzyl(1-p-tolylvinyl)sulfane (19c). Yield (96%), Yellow oil. H NMR
45 (400 MHz, CDCl3): δ 2.40 (s, 3H), 3.93 (s, 2H), 5.21 (s, 1H), 5.47 (s, 1H),
7.20 (d, 2H, J = 7.8 Hz, ArꢀH), 7.27ꢀ7.34 (m, 5H, ArꢀH), 7.47 (d, 2H, J =
8.2 Hz, ArꢀH) ppm. 13C NMR (100 MHz, CDCl3): δ 22.26, 38.22, 112.25, 105 = 9.4 Hz, 1H), 5.29 (t, J = 9.3 Hz, 1H), 5.32 (s, 1H), 5.34 (s, 1H), 7.20 (d,
128.14, 128.20, 129.50, 130.02, 130.14, 137.62, 138.10, 139.45, 145.94
ppm. MS (EI, 70 eV): m/z (%) = 241 [M + H]+. EA calcd (%) for C16H16S:
50 (240.10): calcd. C 79.95, H 6.71, S 13.34; found C 79.94, H 6.70, S
13.32.
2H, J = 7.6 Hz, ArꢀH), 7.47 (d, 2H, J = 8.1 Hz, ArꢀH) ppm. 13C NMR
(100 MHz, CDCl3): δ = 19.20, 20.04, 20.22, 61.42, 67.75, 69,42, 73.25,
75.50, 80.66, 110.92, 126.54, 127.42, 128.04, 134.42, 152.42, 169.91
ppm. MS (EI, 70 eV): m/z (%) = 481 [M + H]+. EA calcd (%) for
110 C23H28O9S: (480.15): calcd. C 57.49, H 5.87, S 6.67; found C 57.46, H
5.85, S 6.64.
Benzyl(1-(4-methoxyphenyl)vinyl)sulfane (19d). Yield (98%), Yellow
oil. 1H NMR (400 MHz, CDCl3): δ 3.34 (s, 3H), 3.76 (s, 2H), 5.18 (s,
55 1H), 5.41 (s, 1H), 6.81 (m, 2H, ArꢀH), 7.04ꢀ7.26 (m, 5H, ArꢀH), 7.58 (m,
2H, ArꢀH) ppm. 13C NMR (100 MHz, CDCl3): δ 37.30, 54.77, 110.49,
2,3,4,6-Tetra-O-acetyl-1-thio-β-D-glycopyranoside(4-
1
trifluoromethylphenylvinyl)sulfane (19j). Yield (88%), Yellow oil. H
114.11, 127.23, 128.62, 128.78, 129.17, 132.30, 137.60, 145.18, 160.43 115 NMR (400 MHz, CDCl3): δ = 2.02, 2.05, 2.09, 2.12, (4s, 12H), 3.82 (ddd,
ppm. MS (EI, 70 eV): m/z (%) = 257 [M+H]+. EA calcd (%) for
J = 10.1, 4.8, 2.4 Hz, 1H), 4.15 (dd, J = 12.4, 2.4 Hz, 1H), 4.28 (dd, J =
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Journal Name, [year], [vol], 00–00 | 5

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DOI: 10.1039/C3RA44499F
2
3
(a) A. R. Katritzky, W. H. Ramer and A. Ossana, J. Org. Chem.,
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Ananikov, N. V. Orlov, I. P. Beletskaya, V. N. Khrustalev, M. Y.
Antipin and T. V. Timofeeva, J. Am. Chem. Soc., 2007, 129, 7252;
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134, 8171; (j) M. Yoshiyuki, S. Hidetake and M. Yasushi, J.
Organomet. Chem., 2006, 691, 3157; see Niꢀcatalyzed: (k) D. A.
Malyshev, N. M. Scott, N. Marion, E. D. Stevens, V. P. Ananikov, I.
P. Beletskaya and S. P. Nolan, Organometallics 2006, 25, 4462; (l)
V. P. Ananikov, N. V. Orlov and I. P. Beletskaya, Organometallics
2006, 25, 1970; (m) V. P. Ananikov, D. A. Malyshev, I. P.
Beletskaya, G. G. Aleksandrov and I. L. Eremenko, Adv. Synth.
Catal., 2005, 347, 1993; see Zrꢀcatalyzed: (n) C. J. Weiss and T. J.
Marks, J. Am. Chem. Soc., 2010, 132, 10533.
12.5, 4.8 Hz, 1H), 4.85 (d, J = 10.2 Hz, 1H), 5.10 (t, J = 9.1 Hz, 1H), 5.12
(t, J = 9.4 Hz, 1H), 5.29 (t, J = 9.3 Hz, 1H), 5.32 (s, 1H), 5.34 (s, 1H),
7.41 (d, 2H, J = 7.2 Hz, ArꢀH), 7.82 (d, 2H, J = 7.2 Hz, ArꢀH) ppm. 13C
NMR (100 MHz, CDCl3): δ = 19.20, 20.04, 20.22, 61.42, 67.75, 69,42,
73.25, 75.50, 80.66, 110.92, 120.42, 126.54, 127.42, 128.04, 134.42,
152.42, 169.91 ppm. MS (EI, 70 eV): m/z (%) = 535 [M + H]+. EA calcd
(%) for C23H25F3O9S: (534.12): calcd. C 51.68, H 4.71, S 6.00; found C
51.65, H 4.70, S 5.58.
65
70
5
1
4
10 n-Propyl(1-phenylvinyl)sulfane (19k). Yield (92%), Pale yellow oil. H
NMR (400 MHz, CDCl3): δ 1.05 (m, 3H), 1.70 (m, 2H), 2.71 (m, 2H),
5.22 (d, 1H, J = 3.2 Hz), 5.50 (d, 1H, J = 3.4 Hz), 7.37 (m, 3H, ArꢀH),
7.60 (m, 2H, ArꢀH). 13C NMR (100 MHz, CDCl3): δ 13.42, 21.80, 34.00,
110.18, 126.99, 128.17, 128.20, 139.73, 145.13 ppm. MS (EI, 70 eV): m/z
15 (%) = 179 [M+H]+. EA calcd (%) for C11H14S: (178.08): calcd. C 74.10,
H 7.91, S 17.98; found C 74.08, H 7.90, S 17.96.
75
80
Benzyl (1-tert-Butylvinyl)sulfane (19o). Yield (84%), Pale yellow oil.
1H NMR (400 MHz, CDCl3): δ 1.14 (s, 9H), 3.68 (s, 2H), 4.60 (s, 1H),
20 5.06 (s, 1H), 6.88ꢀ7.22 (m, 5H, ArꢀH) ppm. 13C NMR (100 MHz, CDCl3):
δ 30.12, 37.35, 38.05, 103.42, 127.32, 128.64, 129.32, 137.20, 158.52
ppm. MS (EI, 70 eV): m/z (%) = 207 [M+H]+.
85
Cyclopentyl (1-Phenylvinyl)sulfane (19p). Yield (91%), Pale yellow oil.
25 1H NMR (400 MHz, CDCl3): δ 1.86ꢀ2.02 (m, 8H), 3.34 (m, 1H), 5.20 (s,
1H), 5.45 (s, 1H), 6.94ꢀ7.50 (m, 5H, ArꢀH) ppm. 13C NMR (100 MHz,
CDCl3): δ 24.83, 33.05, 43.85, 111.60, 127.12, 127.14, 128.30, 140.10,
145.85 ppm. MS (EI, 70 eV): m/z (%) = 205 [M+H]+.
90
95
5
Metalꢀcatalyzed antiꢀMarkovnikov seletivity, see Rhꢀcatalyzed: (a) S.
Shoai, P. Bichler, B. Kang, H. Buckley and J. A. Love,
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2062; see Cuꢀcatalyzed: (e) N. R. Siti, Y. Y. Jackie and Z. Yugen,
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Soc., 2009, 131, 6683; (d) P. J. Baricelli, F. LopezꢀLinares, A. Bruss,
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Ingallina, Organometallics 1990, 9, 3127.
1
30 Phenyl (1-Phenylvinyl)sulfane (19q). Yield (90%), yellow oil. H NMR
(400 MHz, CDCl3): δ 5.35 (s, 1H), 5.37 (s, 1H), 6.86ꢀ7.05 (m, 6H, ArꢀH),
7.45 (m, 2H, ArꢀH), 7.70 (m, 2H, ArꢀH) ppm. 13C NMR (100 MHz,
CDCl3): δ 116.02, 127.40, 127.54, 128.71, 128.85, 129.32, 132.20,
135.05, 139.20, 145.10 ppm. MS (EI, 70 eV): m/z (%) = 213 [M+H]+.
100
105
110
115
120
35 Notes and references
6
7
a Department of Chemistry, Kakatiya University, Warangal, India. Fax:
+91ꢀ870ꢀ2438800; Tel: +91ꢀ9390100594; Eꢀmail:
ravichemku@rediffmail.com
b Department of Chemistry, Satavahana University, Karimnagar, India.
40 Fax: +91ꢀ878ꢀ2255933; Tel: +91ꢀ9000285433; Eꢀmail:
vasamcs@yahoo.co.in
† Electronic Supplementary Information (ESI) available: Catalyst order
experiment
table
and
Catalyst
recycling
table.
See
DOI: 10.1039/b000000x/
45 ‡ Footnotes should appear here. These might include comments relevant
to but not central to the matter under discussion, limited experimental and
spectral data, and crystallographic data.
1
(a) M. Alessandro and N. Daniele, Org. Biomol. Chem., 2012, 10,
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Navacchia, Tetrahedron 1999, 55, 12227; (e) J. W. Chan, H. Zhou,
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Chan, J. Shin, C. E. Hoyle, C. N. Bowman and A. B. Lowe,
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Benati, L. Capella, P. C. Montevecchi and P. Spagnolo, J. Chem. Soc.
Perkin Trans., 1995, 1035; (i) A. Kondoh, K. Takami, H. Yorimitsu
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8
9
50
55
60
R. L. Cowan and W. C. Trogler, Organometallics 1987, 6, 2451.
125 10 C. S. Vasam, S. Modem, S. Kankala, S. Kanne, G. Budige and R.
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130
6
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DOI: 10.1039/C3RA44499F
Graphilcal Abstract
Synthesis of Markovnikov vinyl sulfides via dinuclear Rh(I)-
phosphine catalyzed hydrothiolation of alkynes in aqueous media
5
Shravankumar Kankala, Srinivas Nerella, Ravinder Vadde,* Chandra
Sekhar Vasam *
An efficient regioselective and recyclable hydrothiolation procedure for
the synthesis of Markovnikov vinyl sulfides in aqueous media was
10 developed by employing the waterꢀsoluble dinuclear Rh(I)ꢀPhosphine
catalysts.Catalyst order experiments were used to describe the cooperative
effects between the two metal centers in dinuclear catalysts.
SR2
R1
[Rh(ꢀꢀX)(CO)(L)]2
R2SH
Thiol
R1
aqueousꢀTHF, rt, 0.5 h
Alkyne
Branched
Vinyl Sulfide
L = Hydrophilic Phosphine
X = anionic ligand
This journal is © The Royal Society of Chemistry [year]
Journal Name, [year], [vol], 00–00 |
7